1. Field of the Invention
The present invention relates to the technology field of carrier transport materials, and more particularly to a specific carrier transport material capable of being used as a hole transport layer and/or an electron confining layer of an organic light emitting device.
2. Description of the Prior Art
An organic light emitting diode (OLED) was invented by C. W. Tang and S. A. VanSlyk et al. of Eastman Kodak Company in 1987 and manufactured by a vacuum evaporation method. A hole transport material and an electron transport material (such as Alq3) are respectively deposited on a transparent indium tin oxide (abbreviated as ITO) glass, and then a metal electrode is vapor-deposited thereon to form the self-luminescent OLED apparatus. Due to high brightness, fast response speed, light weight, compactness, true color, no difference in viewing angles, no need of liquid crystal display (LCD) type backlight plates as well as a saving in light sources and low power consumption, it has become a new generation display.
Recently, some interlayers such as electron transport layer and hole transport layer are added into the OLEDs for increasing the current efficiency or power efficiency of the OLEDs. For example, the organic light emitting diode (OLED) 1′ structure shown as FIG. 1 consists of: a cathode 11′, an electron injection layer 13′, a light emitting layer 14′, a hole transport layer 16′, and an anode 18′.
The OLED 1′ shown by FIG. 1 can by fabricated by using a solution process. With reference to FIG. 2, there is shown a flow chart of the solution process for manufacturing the OLED; moreover, please simultaneously refer to FIG. 3, which shows the manufacturing process diagrams of the OLED. As shown in FIG. 2 and FIG. 3, the solution process for manufacturing OLED mainly consists of following steps:
First of all, the process flow proceeds to steps (S01′) and (S02′) for providing a substrate 2′ and at least one template 3′, wherein the template 3′ is formed with a transfer printing pattern 31′. Next, in step (S03′), a plurality of organic light-emitting materials 4′ are coated onto the transfer printing pattern 31′ through an inking process. Subsequently, the process flow proceeds to steps (S04′) for making the organic light-emitting materials 4′ coated on the transfer printing pattern 31′ be transferred onto the surface of the substrate 2′ by a contact printing process. Eventually, at least one light emitting layer 41′ is formed on the surface of the substrate 2′ in step (S05′). Thus, the OLED 1′ shown by FIG. 1 can be mass produced rapidly.
In spite of the solution process can be used for mass produced OLED, the solution process still reveals some shortcoming and drawbacks during practical operations. With reference to FIG. 1, FIG. 2 and FIG. 3, because the manufacturing material of the hole transport layer 13′ and the light emitting layer 14′ is commonly TAPC ((1,1-Bis[4-[N,N′-di(p-tolyl)amino]phenyl]cyclohexane)) and Spiro-2CBP (2,7-Bis(9-carbazolyl)-9,9-sspirobifluorene) respectively, the Spiro-2CBP would dissolve a portion of TAPC when the Spiro-2CBP is coated onto the hole transport layer 13′. Moreover, the same dissolve situation would also occur between any other two layers during the operation of the solution process. Therefore, it can easily know that the solution process cannot used to fabricate a high-quality OLED because of the limitation of manufacturing materials.
Accordingly, in view of the conventional solution process still including drawbacks, the inventor of the present application has made great efforts to make inventive research thereon and eventually provided a carrier transport material for being a hole transport layer and/or an electron confining layer of the organic light emitting device.